Telecommunications chassis, module, and bridging repeater circuitry

ABSTRACT

A telecommunications chassis, module, and repeater circuit for use with signals having data rates including STM-1 (155.52 megabits per second) are disclosed. The chassis provides structures for establishing shielding and heat dissipation for the circuitry modules it contains including an outer and an inner Faraday box with an integrated ventilation pattern for circulating air. The module provides its own structures for establishing shielding and heat dissipation including a Faraday box and a ventilation pattern. The repeater circuit provides the ability to bridge a data signal between a monitor jack of one device and a higher signal level input jack of another device through multiple amplification stages and circuit board structures. The telecommunications chassis, module, and repeater circuit can be used in conjunction.

RELATED APPLICATION

The present application is a division of U.S. patent application Ser.No. 09/812,226, filed Mar. 19, 2001 now U.S. Pat. No. 6,907,230 andentitled “Telecommunications Chassis, Module, and Bridging RepeaterCircuitry,” the entirety of which is hereby incorporated by reference.

TECHNICAL FIELD

The present invention is directed to chassis for holdingtelecommunications modules, the modules themselves, and the repeatercircuitry that may be contained within the modules. More specifically,the present invention is directed to a chassis and module with shieldingand heat dissipation structures and to repeater circuitry for bridgingapplications.

BACKGROUND

A telecommunications chassis provides a mounting structure fortelecommunications modules housing various types of circuitry. Thetelecommunications chassis must provide protection from externalitieswhile also facilitating heat dissipation from the circuitry it contains.The chassis must also attempt to shield its interior fromelectromagnetic interference while limiting the amount ofelectromagnetic interference being emitted from the interior. Forcertain applications, such as providing uninterrupted service duringmaintenance, circuitry housed by the chassis may need to be moved fromplace to place. Thus, portability of the chassis for this type ofapplication becomes important as well. As the data rate being handled bythe circuitry within the chassis increases, the ability to shield andprotect from externalities while dissipating heat becomes moredifficult.

Similarly, with the telecommunications modules that may be housed by thechassis, the circuitry within the module must be protected fromexternalities within the chassis such as heat, flames, loose material,and interference that may be emanating from other circuits also housedby the chassis. Because circuits fail, the module must maintain itsability to be removed from the chassis and replaced while continuing toprotect the circuitry is houses during normal operation. As with achassis, the ability of the module to shield and protect the circuitrywhile dissipating heat becomes more difficult as the data rate beinghandled by the circuitry within the module increases.

Bridging repeater circuits, which may be housed by the modules andchassis previously discussed, must take a low-level electrical monitorsignal from one device, such as a digital signal cross-connect, andrecreate the electrical signal with the data and clock informationintact and at a high level suitable for reception by another device.Bridging repeater circuits are useful where a device has failed or mustotherwise be replaced but a break in service is to be avoided. Thebridging repeater circuit bridges around the faulty device from onehealthy device to a replacement device to establish signal transferprior to the faulty device being disconnected. The bridging repeatercircuit is generally housed by a portable structure which needs toprovide protection from heat and interference so that it may betransported to the locations of faulty devices and successfully createthe output signal. As the data rate increases, the repeater circuit'sability to recover the data and clock information from the low-levelmonitor signal to recreate the output signal becomes more difficult.

Therefore, there is a need for a chassis to provide protection tomodules from externalities and interference while facilitating heatdissipation, even at high data rates and while being portable ifnecessary. There is also a need for a module to provide protection tocircuits from externalities and interference while facilitating heatdissipation, even at high data rates. Additionally, there is a need fora bridging repeater circuit that can recover the data and clock portionsfrom a low-level monitor signal to recreate a high-level output signalrepeating the data and clock information, even at high data rates.

SUMMARY

The present invention includes various embodiments that facilitatetelecommunications functions for electrical signals, including thosewith high data rates such as the STM-1 rate of 155.52 megabits persecond (Mbps). A chassis and a module of the present invention provideheat dissipation and shielding structures that may be used for circuitsoperating at these high data rates. A repeater circuit of the presentinvention recovers data and clock information from low-level monitorsignals to create an output signal with the data and clock informationintact, even at these high data rates.

The present invention may be viewed as a telecommunications chassis. Thechassis includes a shielding chamber having a first and secondhorizontal surface and a first and second vertical surface. The firstand second vertical surfaces are disposed between the first and secondhorizontal surfaces, and the first and second horizontal surfaces andthe first and second vertical surfaces are made of metal and areconductively connected. A vertical backplane has connectors forinterfacing with repeater modules and is disposed between the first andsecond horizontal surfaces and the first and second vertical surfaces.The vertical backplane establishes contact with the first and secondhorizontal surfaces and the first and second vertical surfaces and has aground conductor that is electrically connected to the connectors. Anouter housing encompasses the shielding chamber and the verticalbackplane and has an open side for receiving telecommunications modules.The outer housing has a first cover surface that is substantiallyparallel to but within a different spatial plane from the firsthorizontal surface and has a second cover surface that is substantiallyparallel to but within a different spatial plane from the verticalbackplane. Spacing between the first cover surface and the firsthorizontal surface and spacing between the second cover surface and thevertical backplane form an airspace. A chassis ground conductor is alsoincluded and is electrically connected to the shielding chamber and theground conductor of the vertical backplane.

The present invention may also be viewed as a telecommunications circuitmodule. The module includes a printed circuit board including circuitry.A metal backplate is substantially parallel to but within a differentspatial plane from the printed circuit board. A metal shell has afrontplate, a top surface perpendicular to and extending from thefrontplate, a bottom surface substantially parallel to the top surfaceand extending from a side of the frontplate away from the top surface,and a back surface perpendicular to the front plate and the top andbottom surfaces. The top surface, bottom surface, and back surface eachhas a folded edge that abuts the metal backplate to establish metal tometal contact. A metal jack holder extends perpendicularly from theprinted circuit board and abuts the front plate, top surface, and bottomsurface to establish metal to metal contact along a side away from theback surface. At least a portion of the circuitry is disposed betweenthe frontplate and the backplate and between the metal jack holder andthe back surface.

The present invention may be viewed as a repeater circuit. The repeatercircuit includes an amplification portion that receives a first signalwith data and clock information and increases the amplitude of the firstsignal to generate an amplified first signal. The amplification portionincludes a current feedback amplifier stage and a voltage limitingamplifier stage. A transceiver portion receives the amplified firstsignal with increased amplitude, recovers the data and clock informationfrom the received amplified first signal, and transmits a second signalwith the data and clock information recovered from the first signal.

DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are front and back perspective views of an embodiment ofthe chassis of the present invention.

FIGS. 2A and 2B are perspective and right side views, respectively, ofthe sidewalls and front and rear trim pieces of the chassis.

FIGS. 3A and 3B are an exploded perspective view of inner components ofthe chassis and a perspective view of the chassis without outercoverings with the inner components being installed.

FIGS. 4A and 4B are a rear perspective view of the chassis without theouter coverings and an exploded perspective view of the rear cover pieceand power supply, respectively.

FIGS. 5A, 5B, and 5C are a plan view of the uninstalled rear coverpiece, power supply, and vertical backplane, a perspective of the rearcover piece and power supply showing ground wire connections, and aperspective with the top cover removed to show its ground wireconnection.

FIG. 6 is a rear perspective view of the chassis without outer coveringsshowing ground wire connections and the rear cover piece installation.

FIGS. 7A, 7B, and 7C are an exploded perspective view of the chassis, anexploded detail view of the top outer covering fastener, and an explodeddetail view of the bottom outer covering fastener, respectively.

FIGS. 8A and 8B are perspective views of an uninstalled door and hingeguide, respectively.

FIGS. 9A, 9B, 9C, and 9D are a front perspective view, a rearperspective view, and exploded perspective views of an embodiment of themodule of the present invention.

FIG. 9E is a perspective view of the chassis with a module partiallyinserted.

FIG. 10 is a plan view of the faceplate of the module.

FIG. 11 is a high-level block diagram showing the application of thebridging repeater circuit embodiment of the present invention to anetwork environment.

FIG. 12 is a block diagram of the circuitry of the bridging repeatercircuit.

FIG. 13 is a block diagram of the input section of the bridging repeatercircuit.

FIG. 14 is a circuit schematic of the input section.

FIG. 15 is a block-diagram of the power supply of the bridging repeatercircuit.

FIG. 16 is a top layer view of the printed circuit board showing inputsignal paths.

FIG. 17 is an internal layer view of the printed circuit board showingthe ground plane configuration of connector pins.

FIG. 18 is a cross-sectional view of the printed circuit boardillustrating the six individual conductive layers separated bydielectrics.

DETAILED DESCRIPTION

Various embodiments of the present invention will be described in detailwith reference to the drawings, wherein like reference numeralsrepresent like parts and assemblies through the several views. Referenceto various embodiments does not limit the scope of the invention, whichis limited only by the scope of the claims attached hereto.

Embodiments of the present invention provide a chassis design thatfacilitates high-speed data rates of electrical signals throughimplementation of structures that provide heat dissipation andshielding. Embodiments also provide a module design that furtherfacilitates high-speed data rates of electrical signals throughimplementation of additional structures that provide heat dissipationand shielding. Bridging repeater circuitry embodiments of the presentinvention also facilitate high-speed data rates of electrical signals byimplementing structures that recover the data and clock portions of alow-level monitor signal through sufficient amplification and create ahigher-level output signal repeating the data and clock portions.

FIGS. 1A and 1B illustrate an embodiment of the chassis of the presentinvention. The chassis 100 has a top cover 102, a bottom cover 104, anda rear cover 137 forming an outer housing 105. Front trim piece 120 andrear trim piece 122 fit around the rear edges of the top cover 102 andbottom cover 104, respectively. Front extensions 114, 116 extend forwardfrom the front trim piece 120.

A door 108 is connected to the front extensions 114, 116 through hinges112. The door 108 has a finger 110 that catches on the left frontextension 114 to hold the door 108 closed. A rotatable handle 106 isconnected to the chassis 100 through mount 107. One or more covers 118are mounted on the chassis 100 to isolate the interior of the chassis100 when corresponding modules are not present.

The rear cover 137 has several rows of holes 138 for exhausting heatproduced by the modules housed within the chassis 100. The rear cover137 also has a power socket 130 with electrical connections 132 forreceiving AC power, such as 110V and/or 220V, from an external source.Typically, power socket 130 is internally fused and is switchable toreceive either either voltage. Rails 124, 128 are mounted to the reartrim piece 122 and have feet 126 attached to them. The bottom cover 104has a several rows of holes 136 for passing ambient air into theinterior of the chassis 100. The bottom cover 104 also has several feet134.

FIGS. 2A and 2B show sidewalls 140, 148 of the chassis 100. Thesidewalls 140, 148 are held in position by attachment to the front andrear trim pieces 120, 122. Several holes 150 are located at the top andthe bottom of the left sidewall 148. Similarly, several holes 142 arelocated at the top and bottom of the right sidewall 140.

Ridges 152 are provided in the left sidewall 148, and ridges 144 areprovided in the right sidewall 140. An inwardly recessed region 154 inthe left sidewall 148 and inwardly recessed region 146 in the rightsidewall 140 is created between the sets of ridges 152 and 144. Theinwardly recessed portions 154, 146 are exposed between the top cover102 and the bottom cover 104, and the ridges 152, 144 facilitateattachment of the top cover 102 and bottom cover 104 to the sidewalls140, 148 as discussed below. Handle mount holes 156 are provided in therecessed portions 154, 146 to allow attachment of the handle mount 107.

FIGS. 3A and 3B illustrate the assembly of the interior structures ofthe chassis 100. A top horizontal surface 162 and a bottom horizontalsurface 160 mount to a faceplate 158 and a vertical backplane 164. Boththe top and bottom horizontal surfaces 162, 160 have several rows ofventilation holes 168 that allow air to pass up from the bottom of thechassis 100 through the installed modules and into the top of thechassis 100 where it is channeled between the top cover 102 and the tophorizontal surface 162 and exhausted out the rear of the chassis 100through holes 138.

As can be seen the top and bottom horizontal surfaces 162, 160 havecurled edges 172, 173, 174, and 175 that abut the faceplate 158 and thevertical backplane 164. Each of these surfaces except the verticalbackplane 164 is made of metal, such as cold rolled steel with a zincchromate plating, such that metal-to-metal contact is establishedbetween them. The backplane 164 is typically printed circuit boardmaterial. Likewise, the sidewalls 140, 148 are also made of metal, suchas aluminum, and establish electrical continuity with the top and bottomhorizontal surface 162, 160 through metal brackets discussed below. AFaraday box, or shielding chamber, results which provides shielding forthe modules housed by the chassis 100. The grounding of the shieldingchamber is discussed below. Similarly, an outer Faraday box results fromthe metal top and bottom covers 102, 104 and the metal rear cover 137whose grounding is also discussed below.

The vertical backplane has connectors 166 that allow the modules to beinserted into the chassis 100 and slidably engage connectors 166 toestablish electrical connection. The vertical backplane connectors 166typically provide DC power to the modules from a chassis power supplydiscussed below. The top and bottom horizontal surfaces 162, 160 haveslots 170 that receives fins on the module to guide it as it is insertedand to prevent lateral movement once it is installed. As best seen inFIG. 3B, the faceplate 158 has notches 176 that align with the slots170.

FIG. 4A shows the chassis 100 with the top cover 102 and the bottomcover 104 of the outer housing 105 removed. As shown the shieldingchamber 101 is fully installed in the chassis 100. The shielding chamber101 is held in place by brackets 178, 180 that mount to both the tophorizontal surface 162 and the sidewalls 140, 148. As can be seen anairspace 103 is created by the placement of the shielding chamber 101.The airspace 103 of this embodiment includes the area between the tophorizontal surface 162 and the top cover 102, the area between the rearcover 137 and the vertical backplane 164, and the area between thebottom horizontal surface 160 and the bottom cover 104.

The airspace 103 allows air to enter through the bottom cover 104, risethrough the shielding chamber 103, return to the rear of the chassis100, and exit out the rear cover 137. Air may also enter through thebottom cover 104 and rise directly between the vertical backplane 164and the rear cover 137 and then exit from the chassis 100. As shown inFIG. 4B, the chassis power supply 186 is mounted to the rear cover 137,and the air rising up the vertical backplane 164 may assist indissipating heat from the power supply 186. Because the top cover 102has no holes, any flames imposed on the interior of chassis 100 cannotescape from the top and are, therefore, adequately contained.

Also shown in FIG. 4B, the rear cover has an aperture 184 that is usedto mount the power socket 130. The power socket 130 has rear terminals182 for electrical connection to the power supply 186. Also, a portionof the holes 138 of the rear cover 137 lie directly behind the powersupply 186 and allow it to radiate some heat directly out of the chassis100. Mounting the power supply 186 directly to the rear cover 137 alsopermits easy installation and maintenance of the power supply 186because it can be accessed by simply removing the rear cover 137 and itselectrical connections can be easily made while the rear cover 137 isremoved.

FIGS. 5A, 5B, and 5C show the ground wire connections of the shieldingchamber 101, vertical backplane 164, and outer housing 105, and alsoshows the power connections of the power supply 186. The power supply186 typically receives AC power from the power socket 130 through wires208 and 210 connected to jack 216 of the power supply 186. The powersupply 186 then typically outputs DC power through output jack 218 tothe vertical backplane 164 through wires 212 and 214 where it is thendistributed to each of the connectors 166.

A ground tab 220 of the power supply 186 is electrically connected tothe ground prong 207 of the power socket 130 through wire 206. Theground tab 220 is electrically connected to a ground post 190 of therear cover 137 through wire 204. Ground wires are fixed to the groundpost 190 and ground post 188 of the rear cover 137 through the fasteningassembly 192.

A ground conductor 164′ of the vertical backplane 164 that electricallyconnects the vertical backplane 164 to shielding pins of connectors 166is also electrically connected to the ground post 190 through wire 196.The right sidewall 140 is connected to the ground post 188 through wire198. The left sidewall 148 is connected to the ground post 188 throughwire 202. The top cover 102 is connected to the ground post 188 throughwire 200, and the bottom cover 104 is connected to the ground post 190through wire 194.

The top cover 102 and bottom cover 104 of the outer housing 105 haveconductor tabs 102′ that extend from them for receiving connectors 201of the ground wires 200 and 194. The top cover 102 and bottom cover 104may have a powder coat finish applied and the conductor tabs 102′ remainbare metal to establish electrical continuity with the ground wires 200,194.

FIG. 6 shows the installation of the rear cover 137 and left and rightrails 124, 128 as well as the connections of the ground wires to thesidewalls 140, 148. Because the rear cover 137 is mounted to the reartrim piece 122, the airspace 103 remains between the rear cover piece137 and the vertical backplane 164. The airspace 103 accommodates thepower supply 186.

The ground wire 198 extending from ground post 188 fastens to the rightsidewall 140 through one of the holes 142 in the top of the sidewall140. Likewise, the ground wire 202 extending from ground post 188fastens to the left sidewall 148 through one of the holes 150 in the topof the sidewall 148. The ground wire 196 extending from ground post 190fastens to a mounting hole 197 of the vertical backplane 164 that isalso used to attach the vertical backplane 164 to the bottom horizontalsurface 160.

FIG. 7A shows an exploded view of the chassis 100. As can be seen, thepower supply 186 is placed within the airspace 103, which is maintainedby the spacing between the top cover 102 and top horizontal surface 162,between the vertical backplane 164 and the rear cover 137, and betweenthe bottom cover 104 and the bottom horizontal surface 160. A covering109 may be placed over the faceplate 158 for aesthetics. The door 108has a handle 108′ extending forwardly to facilitate opening and closing.

FIG. 7B shows a fastener for holding the top cover 102 onto the sidewall140. The ridges 144 of the sidewall 140 have a notched end 222 thatreceives a nut holder 224 and nut 226 that fits within the nut holder224. As shown in FIG. 7C, a nut holder 224 and nut 226 has beenpositioned by sliding it within the ridges 144 from the notched end 222to an alignment dimple 230. A screw passes through a hole in the bottomcover 104 to hold it in place. As shown, the top cover 102 and bottomcover 104 are both attached by four of these fasteners.

FIG. 8A shows the door 108 of the chassis 100. The door 108 includes thehandle 108′ which has the finger 110 extending from it. The finger 110passes through a hole in the door 108 so that it may engage the frontextension 114. FIG. 8B shows a hinge guide 232 that mounts to the frontextensions 114, 116. The hinge guide 232 has a hole 232′ for receiving ahinge shaft 112′ extending from hinge 112 that mounts the door 108 butallows it to open and close.

FIGS. 9A, 9B, 9C, and 9D show an embodiment of the module of the presentinvention. The module 234 has a shell 235 that has a frontplate 236, atop surface 250, a bottom surface 262, and a back surface 256. The topsurface 250 has several ventilation holes 252, and the bottom surface262 has ventilation holes 264. The ventilation holes allow air to risefrom the bottom of the chassis such as chassis 100, up through themodules 234 installed in the chassis 100, and into the top of thechassis 100 prior to being exhausted through the rear cover 137. Theshell 235 is typically made of metal, such as aluminum. The edge 266 ofthe top surface 250 is folded, as is the edge 268 of the bottom surface262. The edge 257 of the back surface 256 is also folded.

A metal backplate 254 that is typically made of aluminum mounts to theedges 266, 268, 257 of the shell 235. The metal backplate 254 supports aprinted circuit board 276. Portions 255 of the metal backplate 254extend beyond the perimeter of the printed circuit board 276 and providea surface that can establish metal-to-metal contact with the folds ofedges 266, 268, and 257.

Connector jacks 274 pass signals between the circuitry on the printedcircuit board 276 and external cable connectors (not shown). A metaljack holder 270 is mounted to the shell 235 and to a faceplate 238. Themetal jack holder 270 provides support for the connector jacks 274 withholes 272 that surround the cylindrical sleeve of the connector jacks274. The metal jack holder 270 also establishes metal-to-metal contactwith the shell 235 and with the faceplate 238. The faceplate 238 alsoestablishes metal-to-metal contact with the backplate 254 and the frontedges of the shell 235.

The printed circuit board 276 is enclosed within the shell 235, thebackplate 254, and the jack holder 270 which together form a Faraday boxproviding shielding for the circuitry on the printed circuit board 276.A connector 260 is mounted to the printed circuit board 276 and is inelectrical communication with the circuitry. Typically, the connector260 provides DC power from the vertical backplane connector 166 to thecircuitry. The back surface 256 of the shell 235 has an opening 258 thatallows the connector 260 to pass through. Typically when maximizingshielding, the largest dimension of the opening is one-twentieth or lessof the shortest wavelength of the signal to be handled by the circuitry.

The faceplate 238 has several holes for sending and receiving signals toand from coaxial cables. For a module 234 housing a repeater circuit,such as the bridging repeater circuit of the present invention, amonitor out port 242, a signal out port 244 and a signal in port 246 areprovided for each data channel. As shown, the module 234 houses two datachannels. The faceplate may have a decal 278 attached to it to provide avisual indication of the purpose of each jack, light emitting diode(LED), switch, or other feature provided on the faceplate 238.

The faceplate 238 generally has a fastener 240 for attachment to thechassis 100. The metal backplate 254 has fins 248 located on the top andbottom edges. The fins 248 fit within the notch 176 of the chassisfaceplate 158 and within the slot 170 of the top and bottom horizontalsurfaces 162, 160 shown in FIG. 3B.

FIG. 9E shows the chassis 100 with a module 234 being partiallyinstalled. The fins of the module 234 pass into the slots 170 of the topand bottom horizontal surfaces 162, 160 and notch 176 of the chassisfaceplate 158. The module 234 slides into the opening in the chassisfaceplate 158 and then continues to slide into the shielding chamberuntil the module connector 260 engages the vertical backplane connector166.

FIG. 10 is a closer view of the faceplate 238 of the module 234. Thefaceplate 238 has the ports for monitor output 242, signal output 244,and signal input 246. In addition, the faceplate may have a loss ofsignal (LOS) LED 282 that lights to indicate the signal through signalinput port 246 is not adequately present. An LOS LED 280 may also beprovided to indicate that the signal through signal output port 244 isnot adequately present. Ports and LEDs for both a channel A and achannel B are shown.

FIG. 11 shows an exemplary network environment employing bridgingrepeater circuits of the present invention. A bridging repeater circuit294, which may be channel A or B of a module such as module 234, isincluded as is a second bridging repeater circuit 292 which may be theother channel of the module. The bridging repeater circuits 292, 294 arebeing used to bypass a faulty digital signal cross-connect circuit (DSX)290 without disrupting the signal path between the healthy DSX 288 andthe electrical to optical (E/O) multiplexer (mux) 298. The bridgingrepeater circuits 292, 294 may be housed in a module 234 forinstallation in portable chassis 100, or they may be housed in a modulesuitable for installation in an existing chassis in the networkenvironment such as a chassis with positions for the DSX devices.

Signal transmission through the portion of the network shown passesbetween several digital distribution frames (DDF) 284 that passelectrical signals to the mux 286 where they are multiplexed into anoutput line 285. The mux 286 also receives multiplexed signals from ahealthy DSX 288 through input line 287 and demultiplexes them fortransfer to the several DDFs 284. The healthy DSX 288 has output line304 that feeds into the input of the faulty DSX 290. The faulty DSX 290has an output line 306 that feeds into the input of the healthy DSX 288.

The faulty DSX 290 passes signals to the E/O mux 298 through line 289and receives signals from the E/O mux 298 through line 291. When thefaulty DSX 290 needs to be temporarily or permanently replaced, a newDSX 296 is installed with a line 295 receiving signals from the E/O mux298 that are the same as those signals received by the faulty DSX 290through line 289. The new DSX 296 is also installed with a line 297sending signals to the E/O mux 298. As discussed below, this line 297duplicates the signal being provided over line 291 from the faulty DSX290 to the E/O mux 298.

The bridging repeater circuit 294 receives at its input the monitorsignal output by the new DSX 296 through line 308. The bridging repeatercircuit 294 retransmits the data and clock information of the signalreceived from the new DSX 296 to the healthy DSX 288 through line 302that connects to a make-before-break input jack of the healthy DSX 288used for temporary connections. Because of this completed circuitthrough the bridging repeater circuit 294, the line 306 connecting theoutput of faulty DSX 290 to the permanent input of healthy DSX 288 canbe disconnected from the faulty DSX 290 and then redirected to thepermanent output of new DSX 296 without breaking service in the channel.

The bridging repeater circuit 292 receives at its input the monitorsignal output by the healthy DSX 288 through line 300. The bridgingrepeater circuit 292 retransmits the data and clock information of thesignal received from the healthy DSX 288 to the new DSX 296 through line310 that connects to a make-before-break input jack of the new DSX 296used for temporary connections. Because of this completed circuitthrough the bridging repeater circuit 292, the line 304 connecting theinput of faulty DSX 290 to the permanent output of healthy DSX 288 canbe disconnected from the faulty DSX 290 and then redirected to thepermanent input of new DSX 296 without breaking service in the channel.Once the healthy DSX 288 and the new DSX 296 have establishedcommunication in both channels through permanent connections, bridgingrepeater circuits 292 and 294 can be disconnected from both the healthyDSX 288 and the new DSX 296.

FIG. 12 shows a block diagram of the circuitry 312 of the bridgingrepeater circuits 292 (channel A) and 294 (channel B). The bridgingrepeater circuit input is typically a 75 ohm SMB connector 314, 316 forboth channel A and channel B that receives the monitor signal atapproximately 0.1 Volts (V). The input connectors are electricallyconnected to isolation transformers 318, 320 for channels A and B, andthe transformers have a turns ratio of 1:1. The isolation transformers318, 320 are electrically connected to the amplification portion of theinput section that includes a current feed back operational amplifier322, 324 for each channel in series with a voltage limiting operationalamplifier 326, 328 for each channel.

The voltage limiting operational amplifier 326, 328 of each channelfeeds the amplified signal containing data and clock information, suchas in a coded mark inversion (CMI) format, to an analog data input ofthe transceiver 330, 332 of each channel. The transceiver 330, 332recovers the data and clock information from the signal and creates anoutput signal that repeats the data and clock information, also in CMIformat. The transceiver output is connected to an additional isolationtransformer 338, 340 that passes the output signal to the output jack350, 352, which may also be a 75 ohm SMB connector. The output signalmay pass through a voltage divider network (not shown) prior to reachingthe output jack 350, 352 but the output signal is typically around 2 V.

The transceiver output is also connected to another isolationtransformer 334, 336 that passes the output signal to an additionalvoltage divider 342, 344 that is connected to a monitor jack 346, 348,which may also be a 75 ohm SMB connector. The additional voltage divider342, 344 decreases the output signal received by the monitor jack 346,348 by about 27 dB.

A reference clock 354, which is typically a 19.44 MHz oscillator, feedsa reference clock signal to the transceivers 330, 332. Rather than usinga single oscillator, a separate oscillator for each transceiver 330, 332may also be employed. A low-voltage detector 356 may also be included todetect an under-voltage power supply condition. The low-voltage detector356 feeds a detection signal to a programmable logic device (PLD)control 358.

The PLD 358 also communicates with the transceivers 330, 332 todetermine whether the signals being received or output by thetransceiver are of an adequate level. If the PLD 358 receives adetection signal from detector 356 indicating an improper supplyvoltage, the PLD 358 will trigger a major or minor alarm circuit 360which is in communication with the backplane 364. If the PLD 358receives a transmit or receive signal from the transceiver 330, 332, ittriggers a user LED 362 for channel A or B corresponding to transmit orreceive to provide an indication of the loss of signal.

FIG. 13 shows the input channel and some of the transceiver componentsin more detail for channel A. Two amplification stages are utilized toprovide a sufficient Gain-Bandwidth product to increase the 0.1 Vmonitor signal to 0.5 V peak-to-peak before it is delivered to thetransceiver 330. At relatively high data rates for electrical signals,such as 155.52 Mbps for STM-1 transmission, the bandwidth of theamplification portion must also be relatively large so as to include thehighest frequency for that data rate. The current feedback operationalamplifier, such as the Burr-Brown OPA658, is configured to produce asignificant portion of the overall gain.

A voltage divider network is included with the current feedbackamplifier 322 to provide a source for the voltage limiting amplifier326. The output of the voltage divider has a gain of about 8 dB over themonitor signal. The Burr-Brown OPA658 has a sufficient gain bandwidthproduct to provide the 8 dB of gain through the voltage divider whilemaintaining a frequency response suitable for a 155.52 MHz signal, asmight be received for a 155.52 Mbps data rate.

The voltage limiting amplifier 326, such as the Burr-Brown OPA689, alsoproduces a significant portion of the overall gain. A voltage dividercircuit is included with the voltage limiting amplifier 326 to provide asource for the transceiver 330. The output of the voltage divider has again of about 8 dB over the signal received from the current limitingamplifier 322. The Burr-Brown OPA689 has a sufficient gain bandwidthproduct to provide the 8 dB of gain through the voltage divider whilemaintaining a frequency response suitable for a 155.52 MHz signal.

The voltage limiting amplifier 326 has the additional task of limitingthe voltage received by the transceiver 330. The transceiver 330 has aninput sensitivity range, and the voltage limiting amplifier 326 providesan output through the voltage divider that is guaranteed to be within adesignated range, even if the monitor signal has an amplitude greaterthan anticipated. For the AMCC model S3031B STM-1 transceiver, which isa fully integrated CMI encoding transmitter and CMI decoding receiver,the input sensitivity is from 110 milli-volts (mV) to 1.3 V. Thus, it isdesirable to constrain the output of the voltage divider of the voltagelimiting operational amplifier 326 to fit within this range, and a 0.5 Vpeak-to-peak voltage is suitable. This limit is set-up using a voltagedivider discussed in more detail below.

The transceiver 330 has an analog data input leading to a data/clockrecovery circuit 336. The transceiver also has a loss of signal inputfeeding a LOS circuit 334. The LOS circuit 334 receives the input signalfrom the voltage limiting amplifier stage 326 after it has passedthrough an additional voltage divider network that reduces the signal toabout 0.170 volts to set the floor for adequate signal strength. If thesignal at the analog data input drops below the 0.170 V reference, theLOS out line passing to the PLD 358 is activated.

FIG. 14 shows the input circuit in more detail. A decoupling capacitor382 and power supply filtering capacitors 382′ are included as is aferrite bead 380 to reduce electromagnetic emissions from the powersupply. The current feedback operational amplifier is configured with a402 ohm feedback resistor 384 and a 178 ohm resistor 318 tied to groundand the inverting input to produce a gain of 3.26=(1+402/178). Thevoltage divider 386 of the current feedback stage includes a 22.1 ohmresistor 388 and a 75 ohm resistor 390 that cut the gain to2.52=[3.26*75/(22.1+75)].

The voltage limiting operational amplifier 326 also has power supplyfiltering capacitors 396 and a ferrite bead 398. The voltage limitingamplifier 326 is configured with a feedback resistor 392 of 604 ohms anda 150 ohm resistor 394 tied to ground and the inverting input to producea gain of 5.03=(1+604/150). The voltage divider 408 of the limitingamplifier stage includes a 22.1 ohm resistor 410 and another 22.1 ohmresistor 412 to cut the gain to 2.52=[5.03*22.1/(22.1+22.1)]. The signalpasses through another decoupling capacitor 396′ prior to entering theanalog data input of the transceiver 330.

The low voltage limiting function of the voltage limiting operationalamplifier 326 is configured by an 18.22 kilo-ohm resistor 400 tied tothe −5 V power supply and a 1 kilo-ohm resistor 402 tied to ground. Alow voltage reference input of the operational amplifier 326 is tiedbetween the resistor 400 and resistor 402 to set the low voltage limitto −0.26 V=[−5V*1000/(1000+18,220)].

The high voltage limiting function of the voltage limiting operationalamplifier 326 is configured by an 18.22 kilo-ohm resistor 404 tied tothe +5 V power supply and a 1 kilo-ohm resistor 406 tied to ground. Ahigh voltage reference input of the operational amplifier 326 is tiedbetween the resistor 404 and resistor 406 to set the high voltage limitto +0.26 V=[+5V*1000/(1000+18,220)].

FIG. 15 shows a block diagram of the power supply 368 of the bridgingrepeater circuit. −48V is received from a pin of the backplane connector364 and it delivered through a 0.5 amp fuse 370 to a DC/DC converter372, such as model LW005A. This DC/DC converter converts the −48 V to +5V and supplies the +5 volt to the appropriate circuitry including theamplifiers 322, 326 and transceiver 330. This DC/DC converter 372 alsoprovides +5 V to a second DC/DC converter 374, such as model HPR1000.This DC/DC converter converts the +5 V to −5 V and supplies the −5 V tothe appropriate circuitry.

The +5 V supply is also connected to a reset control device 376, such asmodel DS1810. The reset control 376 sends a reset signal to thetransceiver 330 during power-up and during low voltage conditions. Ifthe +5 V dips below a threshold, such as 4.75 V, then the reset control376 holds the reset line low until the voltage rises above the thresholdand for an additional 150 milliseconds thereafter to reset both thetransmitter and receiver portions of transceiver 330.

The +5V and −5 V supplies are also connected to the under-voltagedetector 356 that connects to the PLD 358. The under-voltage detector,such as model ICL7665S, triggers an output signal when the receivedvoltage dips below 4.45 V to indicate to the PLD 358 that the voltage isbeyond the acceptable range.

FIG. 16 shows a top layer 414 of the printed circuit board, such asprinted circuit board 279 of FIG. 9C, for supporting the bridgingrepeater circuitry 312. The printed circuit board 279 has signal tracesthat lead from the input jack area 416 to the output jack area 436 ofchannel A. A signal trace 418 carries the signal from the input jackarea 436 to the isolation transformer area 420. A signal trace 422carries the signal from the isolation transformer area 420 to the firstamplifier area 424. A signal trace 426 carries the signal from the firstamplifier area 424 to the second amplifier area 428. A signal trace 430carries the signal from the second amplifier area 428 to the transceiverarea 431 to complete the input circuit.

As shown, the signal trace 422 between the transformer area 420 andfirst amplifier area 424 and signal trace 426 between the firstamplifier area 424 and the second amplifier area 428 are individuallylinear. Furthermore, both of these traces 422, and 428 are linear withrespect to one another.

A signal trace 432 carries the signal from the transceiver area 431 tothe second isolation transformer area 433. A signal trace 434 carriesthe signal from the second isolation transformer area 433 to the outputjack area 436 to complete the output circuit.

As can be seen the signal traces from input area 416 to output area 436all lie within the top layer and are therefore disposed within a singlespatial plane. Furthermore, the signal traces leading from the inputarea 416 to output area 436 have a constant width. No test vias or othertrace deformations are present to disrupt the constant signal tracewidth. Placing the signals within the single spatial plane andmaintaining the trace width from input to output improves the noiserejection of the bridging repeater circuit.

For maximizing signal integrity, the length of each continuous piece ofsignal trace should be maintained at 0.25 inches or below, especiallyfor high data rates such as STM-1. Furthermore, potential interferencesources such as the crystal oscillator 354 located in oscillator area417 should be positioned closely to the transceiver portion 431 tominimize the length of the oscillator trace 419. For maximizing signalintegrity, the length of the oscillator trace 419 should be maintainedat 0.8 inches or less.

FIG. 17 shows another layer of the printed circuit board supporting thebridging repeater circuit. This ground layer 437 includes a continuouscopper sheet 440 and shielding pin connections from the pin connectorlayout 438. The continuous copper sheet 440 is tied to the shieldingpins which may be tied to chassis ground, such as through the connector166 that is tied to the ground wire 196 through the ground conductor164′ in chassis 100.

The pins that are for shielding purposes, including pins shown withconnections to the ground plane 440 such as pin 453, surround the pinsthat carry −48 V power and the −48 V return including pins 441, 442,443, 444, 445, 446, 447, and 448 as well as pins carrying alarm relayssuch as pins 449, 450, 451, and 452. These shielding pins such as pin453 in conjunction with the continuous copper sheet 440 establish aground plane that may permeate any gaps between the opening 258 andconnector 260 in the back surface 256 of module 234. As shown, 12 out of55 pins carry power or alarm relays leaving 78% of the pins as shields.

FIG. 18 shows a cross-section of the printed circuit board 460. Theprinted circuit board 460 has several layers including conduction layersand dielectric layers. A solder mask 462 is applied to the top-mostlayer 464, and another solder mask 488 is applied to the bottom-mostlayer 486. A first conductive layer is made of two individual layers, afirst layer 466 of copper and a plating layer 464 made of tin.

Beneath the first layer of copper 466 lies a resin dielectric layer 468.Then a second conductive layer 470 of copper is included. Beneath theconductive layer 470 lies a dielectric layer 472. Beneath the dielectriclayer 472 lies a third conductive layer 474. Beneath the conductivelayer 474 lies a dielectric layer 476. Beneath the dielectric layer 476lies a fourth conductive layer 478. Beneath the fourth conductive layer478 lies a dielectric layer 480. Beneath the dielectric layer 480 lies afifth conductive layer 482. Beneath the conductive layer 482 lies adielectric layer 484. The sixth and bottom-most conductive layer liesbeneath the dielectric layer 484 and includes two individual layers, acopper layer 486 and a plating layer 488 that includes the solder mask.

The dielectric layer 476 has the greatest thickness, such as 28 milsfollowed by the two outer-most dielectric layers 468 and 484 having athickness such as 8 mils. The intermediate dielectric layers 472 and 480have the least thickness, such as 5 mils. The dielectric constant forthese layers is about 4.3. The outer-most copper layers 466 and 486contain about 0.5 oz of copper. The other copper layers 470, 474, 478,and 482 contain about 1 oz of copper.

The conductive and dielectric layers are arranged such that the signalsare on the outer conductive layer 464 to eliminate vias that addcapacitance. The power and chassis ground are layers 474 and 478,respectively, and are separated by the thickest dielectric 476 to limitthe chassis noise that is introduced into the power lines. Conductivelayer 470 is copper ground plane establishing a logic ground. Conductivelayer 482 is another logic ground layer, and layer 486 carries powersupply bypass lines including lines to resistors, capacitors, etc.

While the invention has been particularly shown and described withreference to preferred embodiments thereof, it will be understood bythose skilled in the art that various other changes in the form anddetails may be made therein without departing from the spirit and scopeof the invention.

1. A telecommunications circuit module, comprising: a printed circuitboard including circuitry, wherein the circuitry includes repeatercircuitry receiving an input signal, recovering data and clockinformation from the input signal, and creating an output signalrepeating the data and clock information, and wherein the input signalis a monitor signal, the repeater circuitry including an amplificationportion with a current feedback operational amplifier and a voltagelimiting operational amplifier and including a transceiver portion; ametal backplate substantially parallel to but within a different spatialplane from the printed circuit board; a metal shell having a frontplate,a top surface perpendicular to and extending from the frontplate, abottom surface substantially parallel to the top surface and extendingfrom a side of the frontplate away from the top surface, and a backsurface perpendicular to the front plate and the top and bottomsurfaces, wherein the top surface, bottom surface, and back surface eachhas a folded edge that abuts the metal backplate to establish metal tometal contact; and a metal jack holder extending perpendicularly fromthe printed circuit board and abutting the front plate, top surface, andbottom surface to establish metal to metal contact along a side awayfrom the back surface, and wherein at least a portion of the circuitryis disposed between the frontplate and the backplate and between themetal jack holder and the back surface.
 2. The telecommunicationscircuit module of claim 1, wherein the top and bottom surfaces of themetal shell have a plurality of holes.
 3. The telecommunications circuitmodule of claim 2, wherein the metal backplate, metal shell, and metaljack holder are aluminum.
 4. The telecommunications circuit module ofclaim 1, wherein the monitor signal and the output signal have datarates greater than about 52 megabits per second.
 5. Thetelecommunications circuit module of claim 1, wherein the metalbackplate has mounting fins extending from the edges contacting the topand bottom surfaces of the metal shell.
 6. The telecommunicationscircuit module of claim 1, wherein the back surface has an aperturesurrounding a connector extending from the printed circuit board.
 7. Thetelecommunications circuit module of claim 1, further comprising afaceplate abutting the metal jack holder.